The use of polarised Fourier transform Raman spectroscopy in morphological studies of uniaxially oriented PEEK fibres—some preliminary results

• Published in: Spectrochimica acta. Part A: Molecular spectroscopy 1991, Vol.47 (9), p.1305-1311
• Main Authors: Everall, N.J., Lumsdon, J., Chalmers, J.M., Mason, N.
• Format: Article
• Language: English
• ISSN: 0584-8539
• DOI: 10.1016/0584-8539(91)80220-D

The use of Raman spectroscopy to measure crystallinity in uniaxially oriented poly(aryl ether ether ketone) (PEEK) fibres is discussed. It is shown that previously reported measurements based upon the 1608:1597 cm −1 band intensity ratio are affected by molecular orientation, and as such their application to anisotropic samples must be regarded with caution. The use of the crystallinity-sensitive carbonyl bandhead frequency seems to be less sensitive to molecular orientation and so may be applicable to oriented samples—further work is required to calibrate this measurement with oriented samples of known crystallinity. Some preliminary data on the polarisation properties of the 1597 cm −1 ring mode intensity in PEEK fibre bundles is also presented. These data suggest that the band displays perpendicular rather than parallel character with respect to the fibre long axes. Possible reasons for this effect are discussed. The Raman data indicate that molecular orientation is present in both melt-spun and drawn fibres. The spun fibres appear to be amorphous, but drawing induces significant crystallisation.